The present invention relates to a centrifugation method and chamber for washing and continuous separation of blood constituents, in particular of red blood cells, from washed blood, intended for auto-transfusion during operations or postoperative bleeding in particular, but also being able to be used for deglycerolization operations, for example.
The technique most commonly used for washing and separating blood constituents is centrifugation. Under the effect of the centrifugal force, the various constituents of the blood separate on account of their different densities. This separation takes place naturally in a predefined order, such that the blood constituent of greater density, namely the red blood cells, is always positioned at the greatest possible distance from the axis of revolution of the chamber, whereas the other natural or added constituents of lower density, such as the plasma or a sterile washing solution, respectively, will always be situated nearer this axis than all the other constituents.
The use of automatic devices for autotransfusion allows the blood lost during or after an operation to be recovered by aspiration using a cannula. The aspirated blood is then mixed with an anti-coagulant solution and is then temporarily stored in a reservoir that filters out the largest undesirable particles such as blood clots, bone debris or organic tissue. It is then pumped into a centrifugation chamber. In a first stage, the red blood cells are concentrated by centrifugation, then washed by injection of a sterile solution, for example a saline solution. The undesirable components such as plasma, waste materials, stromata and the sterile solution are then extracted from the centrifugation chamber after sedimentation and are collected in a bag intended to be disposed of, whereas the washed concentrate of red blood cells is transferred into a re-injection bag serving as a buffer reservoir before being returned to the patient.
Document U.S. Pat. No. 5,445,593 describes a device for washing and separation that permits continuous washing. According to this method, the pumping of the blood into the chamber of the centrifugal separator, the injection of the sterile solution into the pumped blood, the extraction of the waste materials arising from the centrifugation, and the extraction of the blood cell concentrate are operations that are performed simultaneously. The chamber of this device is formed by a spiralling annular channel of rectangular cross section whose two end areas are closed. This channel is subdivided along its length into three zones respectively intended for a first separation of the blood constituents, for mixing these constituents with a washing solution injected into the second zone, and for a second separation during which the blood cell concentrate will be extracted from the chamber. The inlets and outlets used for injection and extraction of the blood, of its constituents and of the washing solution are situated on the outer walls of this chamber, which fact necessitates the provision of tubes turning about the periphery of this chamber in the manner of a lasso. This complicates the structure of the chamber, increases its size and does not make it any easier for medical personnel to prepare and use this device.
Moreover, the injection of the washing solution, as is proposed in this device of the prior art, inevitably creates turbulence which, on the one hand, promotes remixing of the blood constituents that have already been partially separated, and, on the other hand, means that it is not possible to utilize the full cleaning potential of the washing solution. The reason is that, because of its radial injection, its low cross section of injection and its low density, the washing solution tends to pass rapidly through the layer of blood under the effect of the centrifugal force and will finally rise to the surface if the blood flow, positioning itself nearer the axis of rotation than the blood. For these same reasons, the radial movement of this washing solution only takes place locally within a limited area.